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epan: Handle truncation of expert infos in the middle of UTF-8 chars 

If the formatted string generated by expert_add_info_format is
truncated by being larger than ITEM_LABEL_LENGTH, it might get
truncated in the middle of a multibyte UTF-8 character.
Check for that, and end the string where the partial character
starts.

Fix #18421
This commit is contained in:
John Thacker 2022-10-10 21:23:38 -04:00
parent 8700e9c407
commit b7249fadd9
1 changed files with 26 additions and 2 deletions
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28
epan/expert.c
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@ -534,6 +534,7 @@ expert_set_info_vformat(packet_info *pinfo, proto_item *pi, int group, int sever
const char *format, va_list ap)
{
char formatted[ITEM_LABEL_LENGTH];
int pos;
int tap;
expert_info_t *ei;
proto_tree *tree;
@ -563,9 +564,32 @@ expert_set_info_vformat(packet_info *pinfo, proto_item *pi, int group, int sever
}
if (use_vaformat) {
vsnprintf(formatted, ITEM_LABEL_LENGTH, format, ap);
pos = vsnprintf(formatted, ITEM_LABEL_LENGTH, format, ap);
} else {
(void) g_strlcpy(formatted, format, ITEM_LABEL_LENGTH);
pos = (int)g_strlcpy(formatted, format, ITEM_LABEL_LENGTH);
}
/* Both vsnprintf and g_strlcpy return the number of bytes attempted
* to write.
*/
if (pos >= ITEM_LABEL_LENGTH) {
/* Truncation occured. It might have split a UTF-8 character. */
char* last_char;
last_char = g_utf8_find_prev_char(formatted, formatted + ITEM_LABEL_LENGTH - 1);
if (last_char != NULL && g_utf8_get_char_validated(last_char, -1) == (gunichar)-2) {
/* The last UTF-8 character was truncated into a
* partial sequence, so end the string where that
* character begins.
*/
*last_char = '\0';
}
/* Otherwise, formatted was truncated at a UTF-8 character
* boundary (and is still a valid string), or else it was
* not a valid UTF-8 string in the first place. In the latter
* case leave it alone too and the UTF-8 validation in
* ftype-string will catch it if enabled.
* (We could sanitize it here too.)
*/
}
tree = expert_create_tree(pi, group, severity, formatted);